This invention relates to a method and apparatus for optical determination of the particle size of a colloidal solution, especially dispersions of synthetic resins, wherein the invention utilizes the scattering of a light beam by the Tyndall effect upon passing through a sample of the colloidal solution.
Various methods are known in the art for determining the size of the particles in a synthetic resin dispersion. One known method is based on a statistical evaluation of photographs produced by the use of an electron microscope. In other known methods, the size of particles in a colloidal dispersion is determined from the dependent angle and/or the wavelength of the scattered light within the collidal dispersion. It is also known in the art to evaluate the radius of a particle in a colloidal dispersion by the statistical evaluation of the Brownian movement of molecules as a function of the radius of the particle. It is a further known practice to use turbidity measurements for determining the particle size in the colloidal dispersion. The results obtainable from turbidity measurements are too inaccurate. Other known measurement procedures have the disadvantage that disproportionately large amounts of equipment and operating time are required to carry out the measurements.
In general, dispersions occur in polydispersed form and the mean particle size is of primary interest. In addition, the particle size distribution is, in many cases, of interest. In recent years, manufacturers and particularly processors, have shown great interest in a rapid determination of the particle sizes of synthetic resin dispersion. That is because knowledge of the particle size provides a basis for conclusions as to the properties of the end product, e.g., a resulting layer of paint. On the other hand, manufacturers of dispersions of plastics have an immediate capability, through suitable procedures and additions, for obtaining desired particle sizes and particle size distributions in a dispersion. In this way, during the production of such dispersions, it is possible to meet the necessary stipulations for obtaining the desired properties in the end product. In the past, a measuring process used for these and other purposes lacked the ability to determine the particle size of synthetic resin dispersion with sufficient speed and accuracy. The present invention is addressed to providing a solution to the shortcomings of known measuring processes and apparatus.